Study On Cathode Properties Of Cobalt / Cobalt Sulfide / Carbon Composite Microbial Fuel Cell

With the increasing energy consumption and environmental issues have become increasingly prominent. Microbial fuel cells(MFCs) have aroused great interest because it can convert chemical energy of organics in wastewater to energy and achieve the purpose of sewage treatment simultaneously. But there are some issues in MFCs such as low output voltage and power density and high cost of cathode catalyst.The oxygen reduction reaction(ORR) of cathode is a key limitation of MFCs.Therefore, for the problems of the cathode we designed two kind of catalyst. The composites were characterized and evaluated by XRD, Raman, XPS, BET, SEM, TEM,and other physical and chemical characterization. Electro-catalytic activity characterized by CV and LSV test. The RDE tests are employed to explore the ORR kinetics and n of the catalysts.The cobalt(Co) chelated polyaniline(PANI) was used as the nitrogen and carbon sources to prepare the N-doped Co/Co9S8/partly-graphitized carbon(Co/Co9S8/NPGC)catalysts. Structure-activity correlations for Co/Co9S8/NPGC were explored by tuning the heating temperature(600–1000oC) to investigate how the active components(Co/Co9S8) and N-doped functionalities(N-species) influence the ORR activity. As temperature increases, the gradual crystallization of Co originating from the reduction of Co9S8 is conducted to form the Co/Co9S8 heterojunction. MFCs with Co/Co9S8/NPGC(800oC) cathode obtained the highest power density(1156 mW m–2)and the lowest charge transfer resistance(11.1 Ω) after 75 d running, which are better than commercial Pt/C(10 wt.%). Although the sole Co9S8 plays a limited role in ORR,the resulting Co/Co9S8 is found to be indispensable to achieve high activity and durability in MFCs cathodes. The dominant ORR pathways of Co/Co9S8/NPGC(800and 900 oC) were the four-electron O2 reduction, which are attributed to the co-existence of pyridinic N, graphitic N and Co-Nx species.PANI was used as the nitrogen and carbon sources before chelated with cobalt added KOH to form the stable chelates. After heating, it was facile to obtain C-N-Mstructure and high degree of graphitization. Enhancing conductivity of catalyst was beneficial to catalytic activity. Co/PGC-900 possesses largest BET specific surface area(354.39 m2 g-1). Co/PGC-900 used as cathode of MFCs existing maximum power density(1201 mW m–2) even at last cycle it just declines 4%. However Pt/C declines11.6%. Using KOH regulated Co/PGC catalysts have lager specific surface area and higher power density.PANI and cobalt can be used as precursor to prepare the N-doped metal sulfide/PGC composites, which is an ideal candidate for Pt/C in MFCs.